Internet traffic company Dyn on Friday warned a third cyberattack is currently ongoing, hours after websites and services across the East Coast were initially shut down.

Dyn told CNBC Friday afternoon the attacks are “well planned and executed, coming from tens of millions of IP addresses at the same time.”

Dyn told CNBC that one of the sources of the attack is coming from devices known as the “Internet of Things” devices such as DVRs, Printers, and appliances connected to the internet.

The company said in a conference call Friday afternoon that the attack is being waged from devices infected with a malware code that was released on the web in recent weeks.

Dyn said it has not heard from attackers and does not know who they are.

“What they’re actually doing is moving around the world with each attack,” Dyn Chief Strategy Officer Kyle York said in a conference call Friday afternoon.

The company’s general counsel, Dave Allen, said during the call the company regularly prepares for scenarios like this.

“We have begun monitoring and mitigating a DDoS attack against our Dyn Managed (Domain Name System) infrastructure. Our Engineers are continuing to work on mitigating this issue,” Dyn said on its website at 11:52 a.m. ET.

A Distributed Denial of Service (DDoS) attack is when a web service is intentionally overwhelmed by traffic from many sources. It is a common method for digital assaults.

Dyn also said the attack impacted its DNS advanced services monitoring for customers, but it later resolved the issue.

It was not known who was behind the distributed denial of service attack.

The Department of Homeland Security told CNBC that it is “looking into all potential causes” of the attack. NBC News reported that one U.S. intelligence official said North Korea had been ruled out as a suspect.

The White House said U.S. authorities are monitoring reports of attack on the internet services company and whether it is a “criminal act,” according to Reuters.